As the injection apparatus, there is known an apparatus which drives a plunger for extruding a molding material into a mold by an injection cylinder (for example Patent Literature 1). The velocity of the injection cylinder (in other words, the injection velocity) is generally controlled by a meter-in circuit which controls the flow rate of a hydraulic fluid supplied to the injection cylinder and/or meter-out circuit which controls the flow rate of the hydraulic fluid discharged from the injection cylinder. The meter-in circuit or meter-out circuit has a flow rate control valve and is usually feedback-controlled based on the velocity of the plunger.
The injection velocity has a large influence upon the quality of the molded article, so is suitably set by taking various conditions into account. For example, in an initial stage of injection, the injection velocity is set to a relatively low injection velocity in order to suppress entrapment of air into the molding material. After that, the injection velocity is set to a relatively high injection velocity for the purpose of filling the molding material into the mold without a time lag relative to the solidification of the molding material.